A method for manufacturing a liquid-surface detection device that detects a level of a liquid-surface of a liquid stored in a container has been conventionally known. As the method for manufacturing the liquid-surface detection device, for example, in a method for manufacturing a liquid-surface detection device disclosed in patent literature 1, positioning grooves with a longitudinal shape are formed on a mounting surface. One end of each positioning groove in a longitudinal direction (a direction in which lead portions of the electronic component project) is a closed end and the other end of the positioning groove is an open end. Side wall surfaces of the positioning groove restrict the lead portion from moving in a direction intersecting the longitudinal direction of the positioning groove, that is, a width direction of the positioning groove. As a result, the electronic component whose lead portions are received in the positioning grooves can be positioned with respect to the width direction of the positioning grooves.